The use of an intermediate transfer member in an electrophotographic (or sometimes known as electrostatographic) machine to transfer toner particles from an imaging member to an image receiving member (for example, a sheet of paper) is well known and is practiced in many commercial electrophotographic copiers and printers.
For example, a toner image is formed on a primary image-forming member (PIFM) such as a photoconductor and is then transferred in a first transfer operation to an intermediate transfer member (ITM) and is subsequently transferred in a second transfer operation from the ITM to an image receiving member. In the second transfer of the toner image, a transfer back-up roller is commonly used behind the image receiving member, and a nip is formed to press the image receiving member to the ITM.
Intermediate transfer members have been designed in various shapes, such as endless belts, webs, sleeves, tubes, drums, and rollers. Many useful rollers comprise an innermost non-metallic core that is generally quite rigid, a cushioning layer (compliant layer), and an outermost toner-carrying layer, for example as described in U.S. Pat. No. 5,828,931 (May et al.).
U.S. Pat. No. 6,377,772 (Chowdry et al.) describes an intermediate transfer member that comprises a cylindrical rigid core member, a compliant inner sleeve member in intimate non-adhesive contact with the cylindrical rigid core member, and a compliant outer sleeve member in intimate non-adhesive contact with the surrounding inner sleeve member. A photoconductive or outermost toner-carrying layer is disposed on the outer sleeve member.
In use, an annular intermediate transfer member is slid onto a cylindrical mandrel in the imaging apparatus and the annular inner core diameter is generally designed to be slightly less than the diameter of the cylindrical mandrel so that a very tight fit is achieved. However, the intermediate transfer member needs to be moved onto and off the mandrel from time to time during normal printing operations.
After a used ITM is removed from a press mandrel, it is replaced with another ITM having acceptable electrical and mechanical properties for more uniform or improved imaging performance. After imaging for many cycles in the printing press, the ITM outer surface can become worn or covered with foreign material, resulting in lessened imaging quality and requiring replacement. To minimize operating cost, it is desirable to reduce the cost of the ITM by reducing raw material costs, especially that of the innermost core. The annular innermost core holds the ITM on the cylindrical mandrel by contact pressure between the cylindrical mandrel and a thin, high-modulus innermost metallic core made to a precise diameter range. The controlled strain results in a tightly controlled level of contact force, while still allowing mounting on the cylindrical mandrel. The required level of precision in size, and the use of nickel with electrical conductivity can increase cost significantly. Such materials are also susceptible to damage in handling and increasing the cost of such materials.
It is desired to have lower cost raw materials that can be fabricated into innermost cores to have a precise annular diameter range, while maintaining that diameter over a long time period through many printing cycles and a normal range of operating environments. For example, it is desired to provide innermost core materials for annular intermediate transfer members that maintain sufficient elasticity so that they can be used through multiple mounting and manufacturing cycles.